To Fight Monsters
by Kenya Starflight
Summary: Something has caused the Sea Kings to become uncontrollably violent, attacking ships and coastal towns. The Navy goes on the defensive, but the pirates decide a more active approach is needed... and the Jaeger program is born. Goofy one-shot that may possibly be expanded in the future.


_AUTHOR'S NOTE: This is what happens when I marathon my way through over 600 episodes of One Piece, fall in love with the characters, and then ponder how to cross it over with my favorite movie. Because EVERYTHING can be crossed over with Pacific Rim. No exceptions._

_These universes meshed together far better than I thought they would... Also some of the pirate ships aren't named in the anime and I couldn't find names on the One Piece Wiki, so I made names up. Enjoy... or at least laugh. _

* * *

The moment the claxon alarms went off the Shatterdome became a riot of activity, despite the hour that some of the less-couth crew members (of which there were many) would call "the ass-crack of dawn." Team members spilled out of their bunks, jerking on clothes before they had even fully awakened or pelting down the halls half-dressed. Crew members surged into the Jaeger bays, activating the titanic mecha and ensuring they were battle-ready. It was as if someone had tossed a lit match into a wasp nest – where there had once been uneasy calm there was now chaos, albeit a semi-organized sort of chaos that struggled to become more organized every moment.

How Portugas D. Ace could sleep through the bedlam was anyone's guess… but his co-pilot wasn't going to let him remain sleeping for long.

"Hey, wake up, Ace!" he shouted, hanging upside-down from his bunk and poking the other Pirate in the ribs. "Rise and shine! It's fighting time!"

Ace groaned loudly and grabbed a pillow, slapping it over his head.

"Wake up!" Luffy demanded, poking him again. "It's a Sea King! Right off the coast of Dawn Island! We're gonna go save our hometown!"

"Mrgl," was Ace's only response.

"Come on, you big dummy!" Luffy performed a little back flip off his bunk and landed on the floor. "We get to go out and punch Sea Kings! Isn't that exciting?"

"Mrrrr." Ace finally emerged from under the blankets, his black hair standing out in a wild mane around his head and his eyes still bleary with sleep. "Why can't those things attack at a reasonable hour in the afternoon?"

"Because where's the fun in knowing exactly when they'll surface?" Luffy replied, tossing his brother and co-pilot a set of clothes. "C'mon, get dressed. You know Marshal Shanks doesn't like it when we're late."

Ace caught the bundle of clothes and set about getting dressed. "Who knows if it's even gonna be OUR Jaeger sent out this time? For all we know they'll decide we're too 'close to home' to fight effectively and send someone else, like Thriller Bark or Dreadnaught Sabre."

"C'mon, you know they have to send Thousand Sunny. It's the best Jaeger in the PPDC! Besides, maybe Sabo'll be there and we can go ashore and play catch-up once we've pummeled the Sea King into submission."

"If the Marines don't chase us off after the fact," Ace reminded him, but he did wear a fond smile as he finished dressing and donned his hat. Together he and Luffy ran out of their quarters and toward the briefing room.

Other Rangers accompanied them on their run to the briefing room, as if the first Pirate team to reach it would be the ones chosen for this mission. Ace could pick out and identify many of them by sight – Zoro and Sanji of Team Going Merry, Law and Bepo of Team Sergeant Pepper, Drake and Dumas of Team Monte Cristo, Eustass and Killer of Team Glasgow Smile, Moriah and Perona of Team Thriller Bark… even his old mentor Whitebeard and old friend Marco, both of Team Moby Dick. Amazing, he thought, that so many former pirates, many of them mortal enemies, had lain aside old hatreds and rivalries, and come together in the face of a worldwide crisis.

It had been four years since the time of the Great Change, when something had altered the legendary Sea Kings that ruled the oceans of their world. No one was quite sure what had happened to cause the change – a virus, a toxin, or something supernatural in nature – but the effects had been disastrous. The formerly reclusive Sea Kings had become uncontrollably violent, attacking ships and coastal towns with reckless abandon, seeming bound and determined to eliminate anything human that tried to enter the water. Thousands had been killed, and untold damage had been wreaked on the islands of the Grand Line.

Such a crisis had not been enough to fully unite the warring factions of pirates and Marines… but it had been enough for each of them to stop fighting and set out to find a solution. The World Government and the Navy, of course, had settled on the coward's way out – building walls around every inhabited island, and forbidding civilian sea travel of any sort. Every island would simply have to learn to be self-sufficient from here on out, and if it meant towns that depended on fishing or imported goods suffered… well, the needs of the many outweighed the needs of the few, right?

The pirates favored a more pro-active solution. The greatest captains of the world came together to declare that from this day on, pillaging and hunting for Gold Roger's treasure would come to an end, or at least a temporary halt. An alliance – the Pirate Protection and Defense Corps, or the PPDC – was forged, and the greatest minds among them set to work to find a way to end the Sea King menace once and for all. Even one of the most notorious minds among them, the sadistic scientist Caesar Clown, had joined the cause, setting aside his experiments to study the Sea Kings in greater depth and discover their weaknesses.

The solution had come from Eustass and Franky – and predictably, their solution was giant robots. Together they designed the first of the enormous mecha they called Hunters, or "Jaegers," a towering metallic giant that Franky, in a fit of nostalgia, dubbed the Going Merry. Despite his enthusiastic opinion that the mecha was just what they needed to defeat the rogue Sea Kings, most pirates had just laughed at him. Even Doflamingo had cracked up laughing, declaring the invention a waste of time.

He stopped laughing in a hurry, as did the entire PPDC, when Sanji and Zoro had piloted Going Merry against a Sea King menacing Dress Rosa, killing it before it could lay a fin on the island.

From that day forward, the pirates set themselves to constructing more Jaegers, training Pirate crews to pilot them, and studying the bodies of dead Sea Kings to determine better and more efficient ways to defeat them. Their base of operations was a huge floating fortress they dubbed the Shatterdome, which could launch up to a dozen Jaegers at a time. They had grown adept at detecting Sea Kings, sending Jaegers to intercept them before they could reach an inhabited island, and defeating them and getting out of there before the Marines showed up to arrest them. And the pirates were no longer seen as menaces to society – they were hailed as heroes, and many islands secretly sent supplies to the Shatterdome to keep it running at peak efficiency.

The fact that so many civilians now hero-worshiped pirates annoyed the Marines to no end – they weren't happy that their efforts to protect humanity from the Sea Kings were being dismissed as useless and counterproductive, nor that their mortal foes were being considered the saviors of mankind. But there was little they could do about it.

Ace stumbled into the briefing room right behind Marco, and the two shared a quick greeting and a friendly slap on the shoulder before Marshal Shanks walked in. The one-armed Shatterdome Commander waited until every team had come in before tilting his hat in greeting and speaking up.

"We've got a Category III Sea King on its way to Dawn Island," he announced. "Biggest one yet, if Caesar's estimates are correct. Armored-type, lobster-like claws, secondary attacks unknown at this time."

"Enough talk," Killer muttered from somewhere behind Ace. "The longer we stand here the closer that thing gets to Dawn Island. Let's go bash it to sushi already."

Shanks raised an eyebrow until Killer's grumbling subsided, then resumed speaking. "Given that this creature is armored, we've decided that a purely physical Jaeger isn't going to be enough. We need a Jaeger with at least one Devil Fruit user aboard, preferably two."

Zoro groaned.

"That means us!" Luffy shouted, slapping Ace on the back enthusiastically. "Thousand Sunny gets to see action!"

"Ow," Ace groaned, rubbing his shoulder. "Calm down, Sunny's not the only Jaeger with two Devil Fruit user Pirates."

Shanks smirked a little. "As a matter of fact, Thousand Sunny is the PPDC's first choice. Luffy, Ace, you two are familiar with Dawn Island, and what areas of it are most vulnerable to attack. Plus you have Devil Fruit abilities that don't cancel each other out. You're Dawn Island's best hope." He nodded at Whitebeard. "Moby Dick will accompany you as backup, just to be safe."

Luffy flashed Ace a "told-you" grin. "Thank you, sir!"

"Just get suited up, Straw Hat," Shanks told him, though a fond grin spoiled his irritated tone. "You've got an island of civilians to protect. Also, we've received word that the Marines are sending a ship to Dawn Island, possibly to intercept you, so be careful."

Ace saluted the Marshal and took off after Luffy, their sandaled feet slapping against the metal floor of the Shatterdome. Despite his earlier irritation at being woken up, excitement tingled throughout Ace's body at the prospect of another fight. Too often the Pirates spent most of their time just waiting for the next battle, and boredom made everyone edgy and irritable. Sometimes fights broke out between Pirate crews if too much time went between Sea King attacks, and though no fatalities had occurred yet, Law was getting tired of having to be pulled from the duty roster in order to play doctor. A chance at some action was a welcome relief from the monotony of Shatterdome life.

They burst into the hangar and ran down the catwalks leading to their Jaeger. The catwalks loomed hundreds of feet in the air, putting them at shoulder level to the towering mecha that protected their world – gleaming titans that stood at attention like so many soldiers, each as unique in appearance as the pirate ships they were named after. Each even bore the Jolly Roger of the ship they were named after on their chest or shoulder, testament to the pride each Pirate team had in their Jaeger. Defenders they might be, but a pirate always remained a pirate at heart.

Marco and Whitebeard veered off toward their own Jaeger, a white-and-silver armored mecha whose cockpit was shaped like a whale's head. Moby Dick was the largest Jaeger built so far, and while some Pirates criticized it as being too slow, it was enormously strong and difficult to damage, with one of the highest kill counts in the PPDC. Ace had almost been chosen to pilot Moby alongside Whitebeard, which would have been a high honor for him – fighting alongside the man he regarded as a father, aboard the Jaeger named after the ship he had called home. But he'd proven a better match with Luffy, and so the honor had gone to another.

Not that he regretted being assigned to Thousand Sunny, he thought as he and Luffy ducked into their Jaeger's cockpit. Fighting alongside his brother was almost as much of an honor as fighting alongside Whitebeard. And while Sunny wasn't as strong or armored as Moby, it made up for it by being lightning-fast and agile. Golden-armored and with the image of a lion's head adorning its chest, it bore sharp retractable blades on its arms and cannons in its torso that could riddle a Sea King with holes before it could blink. And that wasn't even counting the additional abilities its Pirates could bestow upon it…

Chopper waited for them inside Sunny's cockpit, and he helped them into the gear. Ace nodded at the reindeer in thanks before squaring his shoulders back and raising his head, psyching himself mentally for the upcoming fight.

"_Are you two ready?" _Nami's voice sounded from the Den Den Mushi installed in the cockpit.

"We're always ready!" Luffy replied with a grin. "Ready to get in my head, Ace?"

"Always," Ace smirked. "Not that there's much in your head to worry about."

"Hey!"

"_Okay you two, play nice," _Nami ordered. _"Initiating drift sequence in three… two… one!"_

* * *

No two Sea Kings were exactly alike in appearance, but this one was weird even by sea creature standards. It was as if someone had combined a lobster with a moray eel, keeping the most fearsome aspects of both creatures. It had powerful, toothy jaws framed with long, sweeping antennae, and bulbous eyes glared with a mad hunger from its hideous face. Jagged pincers jutted from its sinuous snakelike body, and plates of greenish-brown armor, slick with algae, covered its head, back, and sides. It delivered a throaty roar that made windows shake and the citizens of Dawn Island run screaming as far inland as they could, then surged forward, sending waves crashing into the beach.

It was barely a mile from land when it froze, sensing something behind it. It turned to hiss at the two towering bipedal forms that waded toward it, their fists raised like boxers.

"_Sea King sighted,"_ Whitebeard reported, Sunny's Den Den Mushi picking up his voice from the other Jaeger_. "One mile from shore, but not advancing any further."_

"_Copy, Moby Dick," _Robin reported from the LOCCENT back at the Shatterdome. _"Get as close to shore as you can and hold the miracle mile. Thousand Sunny, keep that thing from making landfall."_

"Yosh!" Luffy replied, nodding enthusiastically. "Let's carve this thing into lunch, Ace!"

"Bring the butter and bibs," Ace replied with a grin. "We're having lobster tonight."

"_Don't get cocky, you two,"_ Shanks advised. _"Just beat this thing and run before the Navy gets here."_

"Yosh," Luffy replied, a bit more subdued but still grinning. "Ready, Ace?"

"Ready." And the two Pirates broke into a run.

Thousand Sunny responded instantly, reaching the Sea King's side in three long strides. Before the creature could do more than turn to face them fully they brought a fist crashing into the side of its head. The monster roared in anger and lashed out with a pincer, trying to grab for Sunny's arm.

"Oi!" Luffy growled. "That's not for you! Steak Knives, activate!"

Ace rolled his eyes. "Who let you name our weapon systems anyhow?"

In response to Luffy's command, blades slid out of Sunny's arms with a wicked _snickt _sound. The Sea King made a second grab for the Jaeger's arm, only to scream in agony as the blade jammed into the fleshy joint of its arm. It backed away, one pincer hanging limply, the other still raised and ready, its entire body swaying from side to side like a cobra's as it looked for another opening to strike.

"I remember these things being harder to beat," Ace noted with a smirk.

He wished he could take those words back a moment later – an alarm sounded in Thousand Sunny's cockpit at that moment, and the Jaeger rocked crazily back and forth before toppling into the ocean. Ace felt a surge of panic as water closed over the cockpit, and for a moment he expected to feel the paralyzing crush of the ocean's power-numbing ability in his limbs, the fatal blow for a Devil Fruit user…

But nothing happened, and the moment of panic ebbed as he and Luffy tried to right Sunny again. The cockpit might be underwater at the moment, but neither Devil Fruit user was physically in contact with the stuff. So long as neither of them had to bail out of the cockpit, they would be safe.

"_Left leg damaged," _the Den Den Mushi reported. _"Situation: dangerous."_

"What the hell'd this thing do?" Luffy demanded. "I'll kill it for wrecking Sunny!"

"It's not wrecked, just damaged!" Ace retorted, wincing in pain as the damage to Sunny made itself known. "We're gonna have to be careful with one bum leg!"

The Sea King hissed and raised its tail – a tail tipped with a wicked barb like a scorpion's tail. Ace and Luffy transferred as much of Sunny's weight to the undamaged right leg as they could, then raised the Jaeger's hands in a "come at me" gesture. Neither of them were done yet, and it was going to take more than a single strike for a Sea King to take them down.

"_Finish it and get out of there!" _Robin advised. _"Marine Ship is approaching Dawn Island fast!"_

"Yessir!" Luffy shot Ace a smirk. "Looks like it's time to get out the big guns."

"Right." Ace raised his hands, concentrating his energy. "Fire fist activate!"

Thousand Sunny's palms faced the Sea King now, and flames began to crackle around its fingers. Another modification that made the Jaegers so deadly – the ability for a Devil Fruit user to channel his own power into the mecha's body, giving it the same abilities as its Pirates without the debilitating side effects of contact with the ocean. And while not all Devil Fruit abilities were compatible with Sea King combat – Drake, for example, still couldn't find a practical application for his Zoan ability in Monte Cristo – the right combination of Devil Fruit powers could make a Jaeger all the more powerful.

The Sea King shrieked as Sunny slammed its palms into its side, leaving a set of charred handprints in its armor. It snapped its remaining pincer, missing Sunny's cockpit by a hand's breadth, and lashed out with its tail to score a line in its armor. Ace and Luffy retaliated by blasting fire into the creature's face, blinding it.

"_Hurry, you two!" _Marco shouted. _"The Navy ship's in sight!"_

"_That's no ship!" _Whitebeard corrected balefully. _"That's…"_

An unholy screech drowned out whatever Whitebeard had to say, and Ace and Luffy screamed in pain as jaws clamped into Sunny's arm. They were yanked backward, a set of tentacles wrapping around the Jaeger's torso and squeezing. More alarms sounded, registering crush damage and warning that any further pressure could rupture the Jaeger.

"What the hell!" Luffy shouted.

"Two of them!" Ace realized. "They don't usually attack in pairs!"

"_Evidently they do now!" _Whitebeard replied. _"Marshal, Thousand Sunny's in trouble! Permission to lend a hand!"_

"_Denied!" _Shanks shouted back. _"You've got a new objective now, Moby Dick – keep the Marines off Sunny's back until it can dispatch the Sea Kings! Try to turn that ship back!"_

"_It's not a ship!"_

"_Then what the hell is it?"_

Ace peered out of the cockpit… and felt his heart nearly stop. Something was approaching out of the mist – and it was the wrong shape to be a ship, even a Navy ship. It approached with a majestic grace, a bipedal form armored in silver-gray and with a sleek, almost caped look to its chassis. On its chest it bore the Navy crest, and the shape of the viewscreen on its cockpit almost made it look as if it were scowling at them. It couldn't be… it just couldn't…

"_Depths below," _gasped Shanks. _"The Marines have a Jaeger."_

A new voice broke in over the Den Den Mushi, one both Ace and Luffy were horribly familiar with. _"This is Vice-Admiral Smoker, pilot of Absolute Justice. Stand down and submit to arrest."_

"We're a little busy here!" Ace shouted back, trying to quell his panic.

"_Moby, hold that Jaeger back!" _Shanks ordered. _"You've got to buy Sunny more time!"_

"_Sunny doesn't stand a chance against two Sea Kings!" _Marco protested.

"_He stands a better chance against two Sea Kings than against two Sea Kings and a Navy Jaeger!" _Shanks retorted. _"Gods, did I really just say 'Navy Jaeger…'"_

Ace could practically feel Whitebeard's anger and frustration vibrating in his voice as he responded. _"Copy, sir."_

Absolute Justice strode forward and raised a hand, making a grab for Moby Dick. The white Jaeger let the silver Jaeger grab its arm, then lashed out with the other fist, clobbering its opponent upside the cockpit. Justice reeled, then lashed out, and soon the two Jaegers were exchanging brutal blows that made the air ring with the impact.

Sunny, meanwhile, still struggled against the tentacled Sea King. The lobster-eel Sea King slunk forward, jaws parted slightly in a savage grin and tail raised for another strike. Ace wondered where it was going to aim for – the chest? The cockpit?

"Nowhere," Luffy snapped. "We're not gonna give it a chance to go stabbity."

"The other one's got our arms tied up!" Ace protested. "How're we supposed to dodge or block it?"

"Aren't you always telling me to use my head?" asked Luffy, and he reared back. "Gomu Gomu Headbutt!"

Monitors in Sunny's cockpit surged with Devil Fruit energy, and Sunny's head rocketed forward as its neck struts stretched to impossible lengths. The domed helm of its cockpit slammed into the lobster-eel Sea King's face, and Ace could feel as well as hear the crunch of bone and cartilage. The beast screamed in pain and backed away, blood dripping from its mangled face.

"Not exactly what I had in mind, but not bad," Ace admitted, laughing.

The lobster Sea King seemed to have had enough of the fight, however, and with a hiss it turned its attention to the shore. It surged forward, a multitude of segmented, insect-like legs on its underside churning up the surf and shore into a sandy slurry.

"No!" Ace squirmed, trying to free Sunny from the Sea King's grip, but to no avail. "It's getting away! Moby, we need help here!"

Moby's cockpit jerked toward Sunny, and that distraction was enough for Justice to grab the white Jaeger in a headlock. Moby thrashed, trying to break free, but the Navy Jaeger was stronger than it looked.

"_Captain Edward Newgate, consider yourself a prisoner of the World Navy," _a crisp female voice – Captain Tashigi – barked. _"Don't resist any further."_

"_Are you idiots?" _demanded Whitebeard. _"How can you think about arrest at a time like this? There are innocent lives at stake!"_

"_You think you pirates are actually helping during this crisis?" _countered Smoker. _"Has it occurred to you ruffians that all your efforts are just making things worse? That you're riling the Sea Kings up by killing off members of their packs, and they're taking their revenge on civilians? Your idiot Jaeger program's doing far more harm than good!"_

"This coming from a Marine who's sitting in an idiot Jaeger as we speak," Ace noted dryly. "If it's an idiot program, why are you copying it?"

"_Because something has to protect Dawn Island until we can get its wall built," _Tashigi retorted. _"Now are you going to surrender?"_

"Hell no!" Luffy shouted. "Because we've got a Sea King making landfall right now, and if we don't stop it, it's going to wreck this place! There'll be nothing for a wall to protect!"

"Let Whitebeard go and let us save the island!" Ace added. "Or else the blood of Dawn Island's civilians is on YOUR hands!"

Justice, despite being a non-sentient mecha, seemed to perk up at that. So they'd managed to touch a nerve with Smoker. That was worth knowing.

"_What's more important right now, Smoker-san?" _asked Whitebeard, as reasonably as if they were sitting down to drinks instead of locked in a life-or-death struggle. _"Sending a couple of pirates to prison, or saving hundreds of innocent lives?"_

That seemed to decide the matter, and Moby staggered as Justice released it.

"_Help Straw Hat and Fire Fist," _Smoker ordered. _"We'll go after the one on land."_

Luffy giggled. "You're not so bad, Smoker-san! For a Marine, anyway."

"_Shut up, Straw Hat," _Smoker huffed.

Moby straightened up and charged the tentacled Sea King. One fist impacted against rubbery flesh, and the creature gurgled and loosened its grip on Sunny. With a flex of its arms the gold Jaeger broke free, and it whirled with both fists raised.

"I feel like fried calamari today, Ace," Luffy noted. "What do you say?"

"You read my mind," Ace replied, grinning. "Fire Fist!"

The squid-like Sea King squealed as two sets of fists pummeled it, one cold iron, the other glowing red-hot. It flailed and lashed out with a multitude of suckered arms, stripping paint from both Jaegers and trying to catch and rip off panels of armor. Neither Jaeger let up, however, and soon the creature's movements grew weaker as the beating took its toll.

Finally the beast went limp, sinking into the water, steam rising from its scorched flesh. Luffy turned and high-fived Ace, which made for a weird moment where Thousand Sunny was essentially high-fiving itself. Moby just shook its cockpit in response before turning its attention to the shore.

Absolute Justice, meanwhile, was standing on the shore, trying to back the lobster Sea King into the water. The monster howled and screeched in frustration as it lashed out with its pincer and tail, but all its attacks passed harmlessly through Justice as if it were made of mist. Which, given Smoker's Devil Fruit ability, wasn't too far off the mark… though its fists were solid enough as it punched and jabbed, driving the creature further back.

"Shall we give him a hand?" asked Ace. "Or do you think he's got this handled?"

"Eh, I want a bit more fun before we go home," Luffy replied. "Rubber man powers!"

The lobster Sea King lunged forward for a final snap at the Navy Jaeger… only to freeze in place as Sunny's fist shot forward on a suddenly elongated arm, its arm blade piercing its head. A shudder ran the entire length of the beast's body, then it sagged to the side, collapsing half-out of the water. Justice gave it one last disdainful kick before turning to glower at Sunny.

"_We had the situation under control, Straw Hat," _Smoker grumbled.

"You're welcome," Luffy replied. "Sorry we can't stay and Jaeger-wrestle, even though I know we'd win, but we're needed back at the Shatterdome. Catch you next time?"

"_He's kind of sassy, isn't he, Admiral?" _asked Tashigi.

Smoker ignored his co-pilot. _"The next time we meet, Straw Hat, you won't get away so lightly. I wouldn't be so light-minded about our future encounters if I were you." _Absolute Justice hesitated a moment, and Ace wondered if it was going to come after them… but Smoker seemed to change his mind, and the Jaeger instead turned and began to walk along the shore, heading back in the direction it came from.

"_Huh… Smoker has a sense of honor after all," _Robin noted with a hint of amusement. _"You don't often find that in a Marine."_

"_Get back to the Shatterdome, Moby Dick and Thousand Sunny," _Shanks ordered, though his voice sounded warmer and friendlier now that the crisis had passed. _"You might have to help Sunny, Whitebeard and Marcos. It took some nasty damage there."_

"Hey, we've gotten Sunny back home with worse damages," Luffy pointed out. "We'll be just fine."

"_All the same, I have a son in there I have to look after," _Whitebeard noted, and Moby put an arm around Sunny, letting it lean against it for support. _"Let's go home."_

Ace wasn't going to argue, and the two Jaegers made for deeper waters and the journey back to the Shatterdome. Another battle over, and another scene of destruction averted. All in a day's work for the Pirates and Jaegers of the PPDC.


End file.
